Styrenic polymers having the syndiotactic configuration (hereinafter, referred to as SPS, occasionally) show excellent heat resistance, chemical resistance, and water resistance. Particularly, SPS has been widely used as the material for various types of molded article to which heat resistance is required because of the excellent heat resistance.
On the other hand, the temperature of heat molding of SPS is higher than conventional thermoplastic resins because of the proper characteristic of SPS. The temperature of the resin during the molding reaches about 300.degree. C. A still higher temperature or a longer residence time in a heated apparatus is sometimes required depending on the condition of molding. When SPS is used singly, a problem arises under such a severe condition in that the resin is degraded by the action of heat and oxygen although SPS has the excellent heat resistance as described above, and a molded article showing decrease in physical properties, such as mechanical strength, and inferior appearance, such as discoloration, tends to be obtained.
Similarly, when a molded article prepared by the single use of SPS is exposed to the air for a long time at a high temperature, a problem arises in that the resin is degraded by the action of heat and oxygen, and the molded article tends to show decrease in physical properties, such as mechanical strength, and inferior appearance, such as discoloration.
For solving the above problems, the present inventors have proposed a resin composition comprising SPS which additionally contains a phenolic antioxidant (Japanese Patent Application No. Heisei 5(1993)-289,290) and a resin composition comprising SPS which additionally contains a phenolic antioxidant and an antioxidant containing sulfur (Japanese Patent Application No. Heisei 6(1994)-384). However, the above problems have not been solved sufficiently.